Cryptosporidiosis is an intestinal parasitic infection that is emerging as a common cause of diarrhea worldwide. The potential for use of Cryptosporidium in bioterrorism is illustrated by the 1993 epidemic that occurred when the Milwaukee water supply became contaminated with the organism and over 400,000 people became ill with diarrhea within a period of a few weeks. Associated with that outbreak were large numbers of hospitalizations and deaths. Based on this potential to cause large-scale epidemics, Cryptosporidium has been classified as a Class B agent for biodefense. According to the World Health Organization, diarrheal diseases are the second most common cause of morbidity and mortality worldwide among children in developing countries and also an important cause of morbidity and mortality in adults, Parasites are more common agents of persistent and chronic diarrhea, which are increasingly recognized as major causes of chronic morbidity. Among the parasites Cryptosporidium, Giardia intestinalis, and Entamoeba histolytica are the most commonly associated with diarrhea. All of these organisms can present with a similar clinical picture, typically with watery diarrhea, yet they differ in terms of optimal diagnostic methods and, more importantly, treatment. The long-range goal for the project is to develop a simple, inexpensive test that can detect all the major diarrhea-causing protozoan parasites that can be performed at the point-of-care, even in developing countries. The specific aims of this project are: Specific aim 1: To optimize an inexpensive, sensitive and specific diagnostic test that can be used for point-of-care diagnosis of Cryptosporidiosis. Specific aim 2: To develop detection methods for Giardia, E. histolytica, Cyc/ospora, and /sospora. Specific aim 3: To assess the sensitivity and specificity of these assays using stools samples obtained in prospective studies of diarrheal disease. To accomplish these goals, we have assembled an interdisciplinary team with proven expertise in point-of-care detection of infectious disease. Dr White's laboratory at UTMB brings expertise in intestinal parasites, clinical infectious diseases and parasite molecular biology and has ongoing collaborations with field studies of diarrheal disease. Dr. Richards-Kortum's Laboratory, at the Department of Bioengineering at Rice University, has focused on applying microfabrication and nanotechnologies to global health problems and has experience in both micro-optical sensors and the use of targeted nanoparticles for molecular diagnostics. The long-range goal for the project will be to incorporate similar techniques to develop a simple, inexpensive test that can detect all the major diarrhea-causing protozoan parasites that can be performed at the point-ofcare, even in developing countries.